The present invention relates to gaming machines, in particular to gaming and slot machines such as poker machines, fruit machines, video gaming machines, video draw card poker machines and the like. In particular, the invention relates to an improved gaming machine wherein the probability of winning combinations occurring may be altered with regard to conventional machines without changing the number of actual symbols or indicia available e.g. the predetermined number of symbols which are available on a rotatable reel or reel-type gaming machine, or alternatively, that the number of physical symbols or indicia may be decreased with a consequential increase in symbol size where the symbols are mounted on a reel, without altering the probability of winning combinations provided on the machine occurring.
The invention particularly, but not exclusively, relates to slot machines common to casinos and clubs where the player inserts coins into the machine and spins at least one rotatably reel by handle or button whereupon the reel or reels become stopped at random, and if the stop symbols coincide with the pay schedule or score card the player is paid a prize. If it is a multi-coin machine the player may buy extra chances or multiply potential winnings.
In a preferred embodiment the present invention applies to slot machines with reels, the stopping position of which is random but under the control of a microprocessor; machines of this type are described in British patent No. 1550732 by PBR and U.S. Pat. No. 4095795 by Saxton.
In a bid to attract players, casinos have offered higher and higher jackpots, and as these are a percentage of revenue the chances of striking a jackpot have to be proportionally less. This was attained in the past, in reel machines, by increasing the number of reels and/or increasing the number of symbols on a reel.
With the development of microprocessor controlled slot machines, where the stopping position of a reel is determined by the microprocessor, a new approach was taken. Telnaes U.S. Pat. No. 4,448,419 selected stopping positions from a virtual reel strip or memory table within the microprocessor which had more virtual positions than there were physical stop positions on the reel itself. By mapping several of these virtual positions to one of the reel symbols, the probability of the reel showing one symbol became different to that for showing others of the symbols. For example, a jackpot symbol can be made to appear with less frequency than other symbols.
With the same intention U.S. Pat. No. 4,858,932 (Keane) selects the real stopping position from a series of random numbers divided into the same number of groups as there are real positions; however the size of each group is unequal thereby causing the appearance of a jackpot or other symbol to be of unequal probability of appearing on a pay line.
Kabushiki Kaisha Universal also describe an arrangement in their Australian Patent No. 561873 in which the slot machine periodically checks the prize value paid by the machine over the preceding period and if this value is too high, the machine adjusts the operation of the machine to make it harder for the player to win. The Kabushiki Kaisha Universal machine is of the type where the reels are stopped under player control by the player pressing a stop button and winning is made harder by introducing a delay in the reel stopping sequence after the stop button is pressed.